[PATCH] r/o bind mounts: elevate write count for ncp_ioctl()

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 53 insertions, 1 deletions

diff --git a/fs/ncpfs/ioctl.c b/fs/ncpfs/ioctl.c
index c67b4bdcf719..ad8f167e54bc 100644
--- a/fs/ncpfs/ioctl.c
+++ b/fs/ncpfs/ioctl.c
@@ -14,6 +14,7 @@
 #include <linux/ioctl.h>
 #include <linux/time.h>
 #include <linux/mm.h>
+#include <linux/mount.h>
 #include <linux/highuid.h>
 #include <linux/smp_lock.h>
 #include <linux/vmalloc.h>
@@ -261,7 +262,7 @@ ncp_get_charsets(struct ncp_server* server, struct ncp_nls_ioctl __user *arg)
 }
 #endif /* CONFIG_NCPFS_NLS */
 
-int ncp_ioctl(struct inode *inode, struct file *filp,
+static int __ncp_ioctl(struct inode *inode, struct file *filp,
               unsigned int cmd, unsigned long arg)
 {
         struct ncp_server *server = NCP_SERVER(inode);
@@ -822,6 +823,57 @@ outrel:
         return -EINVAL;
 }
 
+static int ncp_ioctl_need_write(unsigned int cmd)
+{
+        switch (cmd) {
+        case NCP_IOC_GET_FS_INFO:
+        case NCP_IOC_GET_FS_INFO_V2:
+        case NCP_IOC_NCPREQUEST:
+        case NCP_IOC_SETDENTRYTTL:
+        case NCP_IOC_SIGN_INIT:
+        case NCP_IOC_LOCKUNLOCK:
+        case NCP_IOC_SET_SIGN_WANTED:
+                return 1;
+        case NCP_IOC_GETOBJECTNAME:
+        case NCP_IOC_SETOBJECTNAME:
+        case NCP_IOC_GETPRIVATEDATA:
+        case NCP_IOC_SETPRIVATEDATA:
+        case NCP_IOC_SETCHARSETS:
+        case NCP_IOC_GETCHARSETS:
+        case NCP_IOC_CONN_LOGGED_IN:
+        case NCP_IOC_GETDENTRYTTL:
+        case NCP_IOC_GETMOUNTUID2:
+        case NCP_IOC_SIGN_WANTED:
+        case NCP_IOC_GETROOT:
+        case NCP_IOC_SETROOT:
+                return 0;
+        default:
+                /* unkown IOCTL command, assume write */
+                return 1;
+        }
+}
+
+int ncp_ioctl(struct inode *inode, struct file *filp,
+              unsigned int cmd, unsigned long arg)
+{
+        int ret;
+
+        if (ncp_ioctl_need_write(cmd)) {
+                /*
+                 * inside the ioctl(), any failures which
+                 * are because of file_permission() are
+                 * -EACCESS, so it seems consistent to keep
+                 *  that here.
+                 */
+                if (mnt_want_write(filp->f_path.mnt))
+                        return -EACCES;
+        }
+        ret = __ncp_ioctl(inode, filp, cmd, arg);
+        if (ncp_ioctl_need_write(cmd))
+                mnt_drop_write(filp->f_path.mnt);
+        return ret;
+}
+
 #ifdef CONFIG_COMPAT
 long ncp_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {